No river has garnered more negative publicity than the Selwyn, a once-popular trout fishery and swimming destination for Cantabrians, now polluted in some stretches, prone to drying up in others, and almost bereft of fish.

It was snowing on the Rock and Pillar Range as I stood on a schist outcrop and surveyed the Taieri River coiling like a snake across the floodplain below. The “old water dragon”, as the poet James K. Baxter called it, is one of the strangest rivers in the country. It scrolls northward across the Maniototo Plain, makes a U-turn at the end of the Rock and Pillars, runs southward through the Taieri Gorge, then eases across another set of plains near Dunedin before entering the sea a few dozen kilometres north of its more famous cousin, the Clutha.

Like all rivers that flow through pastoral land, the dragon is less sleek, less robust now than it was when Baxter wrote his lines at Taieri Mouth more than 50 years ago. Its flow is weakened by irrigation takes, and it bears a burden of contaminants on its 200-kilometre journey from source to sea.

Nitrate, phosphate, sediment and microbes—these are the four horsemen of the aquatic apocalypse that ride across the country’s freshwater estate. Their scourges are many: murky river reaches that once ran gin-clear, dead zones in lakes where oxygen levels have dropped to zero, slime-covered stream beds, algal blooms, the steady disappearance of freshwater fish and invertebrates from traditional habitats, the steady rise of faecal bacteria such as E. coli.

An upwelling of public dismay has emerged over the parlous state of freshwater, particularly the pollution of favourite swimming holes, and in extreme cases, those swimming places drying up. Water—both in its quality and quantity—is now the country’s number-one environmental issue. In a 2016 survey, people judged rivers and lakes to be the worst-managed parts of the environment. Almost two-thirds of respondents regarded farming as the main culprit—more than double the number who held that view when the same survey was conducted in 2000.

The country is having a Rip Van Winkle moment, an awakening to a changed reality. It has split the public into polarised factions: town vs country, conservation vs development, individual rights vs the common good. Passions are inflamed. Duelling narratives compete for dominance: Who are we if not a farming nation? Who are we if not a country of healthy rivers and lakes?

“It’s an issue that is both very technical and difficult and also something that resonates with our sense of what’s right and wrong at a visceral level,” said Gary Taylor, executive director of the Environmental Defence Society. “Of course, it’s all very well feeling passionate and angry about the state of freshwater. The question is, what do you do about it?”

Stepping into this fray, seeking a way through it, is a group of scientists attached to a National Science Challenge, one of 11 challenges launched in 2013 to address the most important issues facing the country. Our Land and Water—Toitū te Whenua, Toiora te Wai (let the land be preserved, let the water abound) has $97 million to spend on its mission: “To enhance the production and productivity of New Zealand’s primary sector while maintaining and improving the quality of the country’s land and water for future generations.”

Increase production while improving quality. Is there not an inherent contradiction—or at least a very large assumption—with that objective? Can we really have our environmental cake and eat it too?

This was a question that came up time and again in my visits with scientists in Otago, Canterbury, Waikato, Manawatu and Wellington. It is a question that has come to dominate the country’s thinking on dozens of issues, not just freshwater. Tourism and the conservation estate, hydroelectricity and wild rivers, coal and climate. Arguably, it’s the whole world’s question, as human consumption pushes up against the planet’s thresholds and tipping points.

More than three-quarters of New Zealand’s water take is for agriculture, and most of it ends up sprayed from centre-pivot irrigators onto grazed dairy farms. The high efficiency of sprinkler systems has allowed land previously farmed for sheep and beef to be converted to dairying. The landscape transformation—from brown tussock to green sward—has been dramatic and contentious.

At the Invermay Agricultural Centre in Puddle Alley, Mosgiel, I asked Richard McDowell, chief scientist of the land and water challenge, what he thought about having our cake and eating it too.

“The optimist in me would say, ‘Yes, we can do this’,” he replied. “The realist would say, ‘It’s not possible everywhere.’ There are some places that are just not suitable for certain land uses, where with all the best intentions you cannot decrease contaminants to a level that is acceptable to the wider community.”

One of the challenge’s primary goals, said McDowell, is to shift the way we think about agricultural land from a traditional focus on capability—how much a farmer can profitably produce on a piece of land—to one of suitability, matching land uses to the most appropriate areas of a catchment, based on economic potential and environmental consequences.

“Instead of saying, ‘This land is suitable for dairy or for beef’, we should be saying, ‘This land is suitable for a reasonably high nitrogen loss but needs to have very low phosphate and sediment loss.’ We then look for new ideas on how to best match agricultural options to these load factors.

“In future, you could see a mosaic of land uses in which farmers meet their economic and environmental objectives while the catchment and people outside the catchment also have their objectives met—social, cultural, recreational, and so on.”

Such a change in thinking might take a generation, said McDowell. The meaning of the words ‘farm’ and ‘farmer’ in future could be very different from their meaning today.

Much of the challenge’s work is figuring out the steps needed to get to those next-generation farming systems. The challenge is organised around three targets: obtaining greater value for the primary sector, ensuring land and water are used sustainably, and helping groups work together on managing fresh water.

McDowell’s own research has focused on mitigation—the various ways farmers can reduce the loss of contaminants from agricultural land to fresh water. His group has investigated more than 40 types of mitigation, ranging from straightforward strategies such as fencing and planting streams, capturing and storing effluent and using low-nitrogen feeds, to more ambitious options such as creating wetlands, using materials such as woodchips to remove nitrogen and phosphates from drainage water, and experimenting with how much time stock spend grazing new pastures.

McDowell says farms ought to be able to reduce nitrogen and phosphate leaks by 20 to 50 per cent, at a cost of less than 10 per cent of the farm’s net income.

At Dunedin’s Tomahawk Lagoon, freshwater ecologist Marc Schallenberg throws a sampling net to measure the numbers of daphnia, the water flea. Daphnia are an aggressive grazer of algae, and high numbers are an indicator of good ecosystem health, says Schallenberg. “If they disappear, the algae flourish and we can end up with algal blooms.” The more sediment and nutrients entering a lake, the greater the chance of blooms.

One technology that is seeing rapid development and uptake is variable-rate irrigation. Adjusting the volume of irrigation water according to soil conditions can substantially reduce drainage, cutting the amount of nitrogen and phosphate being lost by up to 70 per cent, said McDowell.

“The next step is to use moisture sensors in cropland to essentially eliminate drainage. If there’s no drainage, there’s no leaching. All the moisture and nutrients being applied through irrigation stay within the root zone to be utilised by the plants.”

The more transformative changes to farming practice, such as mixing and matching their operations according to land-use suitability, probably won’t happen until the value of their products rises.

Marketers, economists and industry leaders frequently opine that New Zealand agriculture needs to move from being an exporter of mainstream commodities to a supplier of premium products. Some challenge scientists told me they would prefer to see the challenge’s mission statement switched from enhancing productivity to enhancing value.

“Productivity is so dated,” one said.

McDowell noticed I was wearing a pair of merino-wool shoes. “There you go,” he said. “Merino has been a great example of how to get better value from an existing land use. The next step is using the value chain to incentivise change in farming practice. Take that step and you haven’t got just a handful of high-country farmers involved, but potentially thousands of farmers going down that route.”

As many challenge scientists pointed out, New Zealand’s export earnings from agrifood amount to just a seventh of their retail value. A lot of people are clipping our ticket along the way.

Reduce the footprint, increase the value—that’s the dream everyone seems to be pinning their hopes on, a kind of economic upward mobility. “It’s the thing that brings everyone together,” one scientist told me. “It’s the New Zealand story—having a healthy environment and being high-end producers. What’s not to like?”

Ken Taylor, the challenge’s director, has no illusions about the difficulty of achieving it. He’s been involved in environmental management for 30 years.

“What I see in the challenge is a very optimistic perspective of increasing value, using smart technologies, applying mitigations, choosing the right land use. But what if there’s also a need to de-intensify? What if we’re too close to environmental limits? What if we’ve reached ‘peak cow’?”

[Chapter Break]

Across the hill from Mosgiel, at the neck of land where Otago Peninsula joins the city of Dunedin, I met Marc Schallenberg, a University of Otago freshwater scientist and president of the New Zealand Freshwater Sciences Society. We were sitting in my truck next to Tomahawk Lagoon—a pair of lagoons, actually, shaped like lungs, with a pulmonary vein draining into the Pacific. As the rain drummed on the roof and a biting southerly whipped up small whitecaps on the lagoon’s grey water, Schallenberg—an expert on lakes and estuaries—told me we are indeed reaching, and breaching, environmental limits.

“Ecosystems can absorb a certain amount of pressure or abuse or pollution, but then something flips and there can be a rapid change—a regime shift.”

Tomahawk Lagoon goes through such changes every few years, said Schallenberg, switching from a clean-water state dominated by aquatic plants, such as seagrasses, to a turbid state brought on by algal blooms.

This lagoon remains in flux, whereas some lakes have undergone a permanent shift—most dramatically Te Waihora, or Lake Ellesmere, Canterbury’s largest lake. In 1968, the storm that sank the Wahine wrenched out most of the aquatic plants that had been stabilising the lake’s sediment and absorbing nutrients seeping into it from farmland. Without the seagrasses, algae gorged on nutrients and bloomed across the lake.

“Ellesmere flipped from having lots of plants to almost no plants, and algae and toxic cyanobacteria have dominated the lake ever since,” said Schallenberg.

There had been flipping before, he said, but the plants always bounced back. This time, they didn’t. With increasing farming pressure, nutrients flowing into the lake reached such high levels that the submerged plants couldn’t compete with the microscopic algae. The lake hasn’t recovered since 1968.

Availability of water marks a division in the Mackenzie country between irrigated dairy pasture and traditional tussock-dominated grazing land. It reflects a social division, too. The Mackenzie Basin has long been recognised as an outstanding natural landscape with unique and threatened ecosystems, and attempts to preserve these values have pitted farmers against others, including tourism interests that derive considerable income from the region’s popularity with visitors.Nutrient enrichment from upstream agriculture pushed Canterbury’s largest lake, Te Waihora/Lake Ellesmere, to a tipping point in the 1960s, when it suddenly shifted from a clear-water state dominated by aquatic plants to a turbid state dominated by algae. The cost of restoring the lake—which has the greatest number of bird species of any habitat in New Zealand—has been estimated at upwards of half a billion dollars.

As with climate change, knowing how close you are to a tipping point is difficult. It’s a matter of measuring the signals and estimating the size of the environmental buffer, or ‘headroom’. As headroom diminishes, risk increases, and so should caution.

“We can incentivise, we can find new markets, we can require polluters to pay. That’s fine if you have a lot of headroom, but if you’re approaching a point where you have to claw back—say a catchment is over-allocated in terms of nutrients, how do you do that? How do you distribute the cost of allocation throughout a catchment? What is the political mechanism for stepping back from the edge?”

The regulatory challenge of agricultural contamination is that it is incremental and cumulative, and its origins are difficult to trace. It isn’t possible to measure pollution in sufficient detail to determine what each farmer is contributing.

“Imagine a simplified system where the nitrate leaching from each farm goes into a pipe and all the pipes lead into a big pond—you could work out each farm’s contribution,” he said. “But there’s no single pipe coming out of a farm, and people are doing things very differently on their farms in terms of the crops sown, the amount of fertiliser, the stocking rate, the soil type, the nature of the groundwater flows, the presence or absence of attenuating wetlands, and so on.

“If we had perfect knowledge and continuous monitoring, we might be able to work out how much leaching was coming from each farm, but it’s still a collective issue, because what you require from one farm to meet a water-quality target depends on what every other farmer in the catchment is doing.”

Either we could measure and model the land-water system to the nth degree, he added, or we could take a precautionary approach to make sure we don’t reach any tipping points. Being careful makes economic as well as ecological sense, he said.

“Trying to recover something you’ve lost is far more expensive than stopping it happening in the first place. Especially if your whole reputation, your brand advantage over the rest of the world, rests on the perception of purity and pristineness.”

One possible solution would be to subsidise environmental protection in the primary sector, as is done in Europe.

“If we think agriculture is really important and we want to protect our environment—have our cake and eat it, too—how about we pay the farmer to farm sustainably?” he suggested. “We keep expecting some overseas consumer to pay a premium so we get to keep our nice clean swimming holes. Why aren’t we paying for it, if it’s so important to us?”

At the moment, it’s the environment that pays—by bearing the impact of agricultural contaminants, he said. “We should admit that our polluted waterways are, in effect, a subsidy to the intensive farmer.”

[Chapter Break]

For most New Zealanders, the emblem of freshwater decline has four legs and an udder. Ever since Fish and Game’s ‘dirty dairying’ campaign began in 2002, it has become impossible to see cows grazing beside a stream (or, heaven forbid, standing in a stream) and not imagine them as effluent delivery systems. Less ruminators than contaminators.

Drive through Canterbury, as I did, and dairying is in your face. It’s like driving through a green desert, with irrigators like silver centipedes lining the road, their tail ends tethered to hydrants. It was early winter when I passed through, so most were stationary, their work done for the year. Though I did see one or two sprinkling golden rain.

“The landscape has become radically simplified,” says Christchurch environmental historian Eric Pawson. “Hedgerows and shelter belts have come out. Patches of plantation forest have gone. People have seen the countryside changing before their eyes.”

In Canterbury, Southland and parts of Otago, dairying appeared suddenly and spread rapidly, so it is associated with landscape transformation, with all the challenging implications that has for people’s sense of place.

“With the combination of good milk prices, cheap land and new irrigation technology, suddenly you could grow grass anywhere you liked,” said Ken Taylor. “It was a massive and sudden change. People who haven’t flown in to Christchurch for a while tell me they used to love looking out the aircraft window at all the little multicoloured squares of crops on the plains. Now, instead of little squares, it’s big green circles.”

I asked Richard Muirhead, who is one of only a handful of New Zealand scientists who specialise in microbes such as E. coli, if dairying is the environmental villain it has been made out to be.

“In terms of nitrate, yes, dairy is a big contributor,” he said, “driven by the urine patch and the amount of fertiliser.” (Those urine patches—like dark-green melanomas freckling the pasture—can drop up to a tonne of nitrogen per hectare on to the soil. Growing pasture cannot handle that kind of nitrogen load, so it readily leaks out of the root zone.)

“And in terms of intensification, yes, dairy’s got that, too,” he added. (The national dairy herd has doubled in size in the past 20 years.) “But dairying occupies a small proportion of land area. A lot of intensification has happened in sheep and beef as well. In Southland, for instance, more than half of the contaminants coming to the mouth of their rivers are from sheep and beef farms because of the sheer area of land.”

Much of that land is steep, too, where soil damage and sediment runoff are more of a problem than in flatter dairy pasture. And it’s in the steeper upland parts of catchments that most rivers have their origins. They start off as narrow capillaries, and it is at that size—so-called first-order streams—that the interaction with land, and the potential for contamination, is greatest. While the dairy industry says its Water Accord has led to stock exclusion from almost all streams defined in the vernacular as “wider than a stride and deeper than a Red Band gumboot”, catchment modelling by McDowell and others suggests more than three-quarters of the country’s streams are smaller than that, and are not covered by the accord’s fencing requirements or the government’s Clean Water package. They are prime candidates for contamination, yet fencing them is probably not an option.

“If you were to fence off all the streams in dry-stock country, the amount of wire you would need would stretch 30 times round the globe,” said John Quinn, NIWA’s chief scientist for fresh water and estuaries. “We need cleverer ways of managing how sheep and beef interact with water, such as reticulating water and managing shade and shelter to reduce the incentive for animals to go to streams. There are some natural livestock behaviours we can draw on in the design of paddocks.”

New technologies such as virtual fences could also be major stream savers. In one version under development in Australia, called eShepherd, livestock wear solar-powered GPS collars that emit an audible warning when the animals approach the virtual boundary, and an electric shock if they cross it.

“I expect to see more and more use of satellites to gather data about where animals are,” said Quinn. “And as forecasting gets more fine-scaled, we will be able to advise farmers that there’s likely to be a runoff event in the next 12 hours. Maybe in the future we’ll be able to shift the animals digitally. There are better ways than 30 times round the world with fencing wire.”

Yes, there is a general correlation between land-use intensity—be that measured by stock numbers or tonnes per hectare of product—and contaminant losses to waterways, McDowell said, “but a non-intensive system, such as an organic farm on steep country, could be leaching more phosphate than an intensive operation on flatter land.

“With variable rate irrigation and careful application of fertiliser, a dry-stock farmer who converts to dairying could increase profitability from something like $100 per hectare to $10,000. But nutrient emissions might go down by as much as a third.”

So much depends on the land in question. McDowell gave me another example:

“Two farms, one in Northland, one in Southland, produce the same amount of product with the same number of animals. But one has half the emission profile of the other. Why is that? We don’t yet know.”

Talking to challenge scientists, I kept being reminded that you can look at water quality through a glass-half-full or a glass-half-empty lens. Economic opportunity or environmental limit. Which of this should predominate in New Zealand’s thinking and policy making?

As a thought experiment, I tried flipping around the two components of the challenge’s mission statement, so that it reads like this: “To maintain and improve land and water quality while enhancing the value of New Zealand’s primary sector.”

The order makes a difference, I think. Not least, it affirms a priority embedded within the Resource Management Act, that environmental bottom lines exist in the real world, and that human economic activity must be adapted to them—and not the other way round.

[Chapter Break]

There is a lot more at play in these issues than markets, soil types and farming technologies. Farming’s social licence to operate is being questioned by the wider community, which is predominantly urban. To many farmers, the loss of their social legitimacy has come as a shock, as inconceivable as if the All Blacks were to lose theirs.

Peter Edwards, a political scientist with Scion Research, told me that social licence to operate is a term that emerged from the mining industry in the 1990s.

“The idea behind it is community acceptance. Communities take on a certain level of risk from someone wanting to develop a resource, whether it’s intensive dairy farming, cutting down trees, digging a big hole and dragging minerals out—and they should get some sort of benefit, or at least recognition, for shouldering that risk.”

The core elements of social licence, said Edwards, involve a community feeling it has a say in the decision-making around a project, believing the benefits are distributed fairly, and trusting the company will follow through on its promises and engage with the community in a meaningful way.

Interestingly, regulatory approval does not guarantee social licence. A company may have a legal licence to operate, but if it lacks a social licence, its operations might be short-lived.

The simplest way to prevent contaminants reaching waterways is to keep stock out. Mike Salvesen, who farms beef and deer and raises dairy heifers on a hill-country station near Mt Somers, is progressively fencing the streams on his property.

Social licence to operate is not only constantly evolving but contestable, with various interest groups seeking to influence a community’s position on an industry’s legitimacy.

Many farmers have grasped that the winds of public opinion about agriculture, and especially dairy farming, have shifted and, by and large, grown colder.

The outgoing president of Federated Farmers, William Rolleston, tried to articulate the importance of social licence in a speech at the National Fieldays in 2015.

“We are a nation of farmers,” he said. “The alignment of the values between farming and the community has been implicit for the last 150 years. So it is a surprise to many farmers today that this alignment has come unhinged and that we should even be considering farming’s social licence to operate.”

He went on to warn his audience that community anger can have far-reaching effects.

“The outrage factor will trump science and translate into regulation, even legislation—the formal curtailment of our social licence to operate.”

Whereas social licence used to refer to local communities and industries, today the ‘community’ in question is national, even international, if global consumers are considered.

In response, some farmers and industry groups have concluded they need to ‘tell a better story’ to earn back public approval, but Edwards said that’s missing the point. The key ingredient is trust, and it surprises him how little community engagement is undertaken by primary producers and agricultural organisations.-

High-tech mitigations include variable-rate irrigation systems, which apply water based on the pasture’s moisture needs, reducing nitrogen and phosphate losses by up to 85 per cent. Ashburton sharemilker Stuart Russell adjusts an irrigator based on moisture data sent to his smartphone from a pasture sensor.

This is the core aspect of his work for the land and water challenge. Often, he added, all that a community want is to feel that their input on how things should be done is taken on board, that they’re being listened to. It doesn’t seem too much to ask.

Another sector of the land and water challenge is coming at the same goal from the community side, figuring out how to foster collaboration between the disparate values, expectations and aspirations that people hold when it comes to making decisions on how to use land and water.

Melissa Robson, an environmental scientist with Landcare Research in Lincoln, is part of this initiative. When we met, I noticed she was carrying a tote bag with the slogan ‘Keep calm and read Jane Austen’. It seemed appropriate, given the discordant rhetoric surrounding freshwater: a lot of hurt pride in the farming sector and a good deal of prejudice in the minds of some river activists.

I asked her how collaboration can advance while—as she put it in a briefing document—“adversarial processes have dominated allocation and consent applications, leading to stalemate and inaction”.

She pointed to the fact that the government now incentivises collaborative planning, giving it a faster track through the thickets of policy-making.

Robson contrasts this new approach with the old-school process—“council gets information, defines the issues, makes a decision, then defends its decision”. With the collaboration method, she said, councils or the government become arbiters of community input. “They say, ‘Okay, this group represents the various values in the community, and we will attempt to broker their recommendations and knowledge’.”

But Robson warns collaboration can hit a brick wall of institutional inertia.

[sidebar-1]

The Land and Water Forum, the country’s largest collaborative exercise involving more than 60 organisations, has struggled with the problem of getting its hard-won consensus recommendations translated into government policy. Two of the forum’s environmental member groups, Fish and Game and Forest and Bird, made a public show of withdrawing from the forum this year, saying the government had largely ignored the forum’s recommendations, and the collaborative approach had failed.

On one point, however, the forum has succeeded.

“The biggest gift to the nation from the Land and Water Forum has been the National Policy Statement for Freshwater Management,” said Ken Taylor, who is a forum member. “It is forcing regional councils to do a lot of things some wouldn’t previously have done, including getting to know their catchments in order to manage them properly. Just setting nutrient concentration objectives in streams without any reference to the intensity of land use that is taking place around them is nuts. But some councils have done that for years. Now councils are required to set actual limits on water quality and quantity, and that has changed the game.”

[Chapter Break]

Climate change, the elephant in every room, the universal reality check, thrusts itself into the freshwater picture at this point, because no amount of matching primary production to land type and no amount of nutrient mitigation sidesteps the problem of livestock carbon emissions. And the very same markets that economists in the land and water challenge are expecting to pay higher prices for products with sound environmental provenance will also be demanding a low carbon footprint.

Quinn says carbon trading could fund water-quality improvements. At NIWA’s offices in Hamilton, he told me that by planting erosion-prone land in pine, a marginal hill-country farm might sequester 25 tonnes of carbon dioxide per hectare per year.

“At the current carbon price of $16 a tonne, that’s $400 per hectare per year. The freshwater solutions can be paid for by the carbon dividend.”

New Zealand has international emissions-reduction targets to meet (or pay for not meeting them), and this will have a bearing on land-use choices and farming systems. Mike Hedley, professor of soil science at Massey University’s Institute of Agriculture and Environment, says two-thirds of the country’s ruminant emissions come from dairy.

“While the dairy industry has been heralding the efficiencies it’s been gaining—more production per unit of greenhouse gasses emitted or nitrate leached—the overall area in dairying and the number of cows per hectare have increased, so total emissions have gone up.”

Hedley says it is imperative that the two issues—greenhouse-gas emissions and water quality—are considered together.

With winter approaching, Trevor Monson milks his herd for the last time before drying them off. He and his wife Stacey manage a 400-hectare property near Methven, milking 1500 cows. Modern dairy operations such as this one use a range of mitigations to minimise their environmental footprint, such as applying effluent back onto the land (instead of into waterways), fencing streams, planting riparian buffers and using feed pads to keep cattle off pasture during cold, wet months.The use of winter forage crops such as fodder beets, here being eagerly consumed by a herd on Lincoln University’s research farm, is a New Zealand innovation that has seen rapid uptake by dairy farmers, and is now spreading to sheep and beef. Cattle grazed on fodder beet may excrete less nitrogen to the environment than cattle fed traditional winter brassicas such as kale—one of several lines of inquiry by New Zealand scientists working to improve agriculture’s environmental performance.

Rivers can be seen as a proxy for climate. Modern societies have treated both as bottomless pits, receiving the waste products or uncaptured superfluities of their activities. Agricultural nutrients, industrial wastes, urban detritus and other outputs flow into the waterways. Greenhouse gases from combustion and other chemical reactions flow into the atmosphere. In both reservoirs, thresholds have been breached.

As for global warming’s physical impacts on our waterways, Rob Davies-Colley, a principal water-quality scientist at NIWA, predicted an “invidious interaction with water quality later this century”. Reduced flows in the drier eastern regions and higher river temperatures throughout the country will drive spiralling nutrient concentrations and more frequent and widespread oxygen stress.

In addition, the cleanest streams are likely to have the most problems with algal blooms as global temperatures rise, because a clear river allows better light penetration than a turbid one. Global warming will increase water temperature in tandem with air temperature. A clear, warm, nutrient-enriched waterway is like a greenhouse for algae.

Particularly problematic is that it is the lowland rivers with the greatest enrichment of nitrogen and phosphorus that have seen the largest improvement in water clarity, and are therefore at greatest risk of blooms. And where do people like to swim? Lowland rivers.

Put all these factors together and there’s a perfect storm coming the way of livestock industries in New Zealand, of which environmental impacts are only a part.

There’s also the effects of climate change on the industry, the vulnerability of its products to exchange fluctuations and price swings, the substitution of meat and dairy products with plant-based alternatives, and the erosion of farmers’ social license to operate.

And if there’s a storm coming for livestock farmers, there’s another one on the horizon for waterways, despite the mitigations farmers are putting in place.

There’s an ominous phrase some water scientists use called “the load to come”. They’re talking about places where nutrients are lurking in groundwater, taking their sweet time in their underground journey from one place to another.

Scott Larned, a NIWA ecologist with a strong interest in how ecosystems interact with water, told me it can take 60 to 100 years for rainwater falling on the upper Canterbury Plains to percolate to the ocean, picking up and transporting contaminants from farmland as it moves through the ground.

We were standing next to the Halswell River, which runs through Lincoln, at the time. He said that if you took a beaker of water from the Halswell and aged every molecule, the average age would be 60 years, which means the water bears the signature of 60-year-old farm activities.

“Since that was prior to a lot of intensification,” he said, “it means we haven’t seen the most contaminated groundwater yet.”

Davies-Colley agreed the full impact of agricultural intensification on river-water quality will not be felt for several decades: there is still a half-century of nutrients to leak into rivers.

When it comes to water quality, “we all live downstream,” says Canadian environmentalist David Suzuki. It is relatively easy to prevent pollution of waterways from concentrated sources such as a milking shed, but much harder to contain contamination from leaky soils. New Zealand looks to innovative science, strong regulatory frameworks and an energised public to protect this precious commodity: fresh water.

Meanwhile, the government has set a goal of doubling exports by 2025, which could mean more hooves on paddocks, more fertiliser and supplemental feed, and more risk of eutrophication to rivers.

How can New Zealand avoid a hard landing on freshwater, I asked Davies-Colley.

“Across-the-board recognition that land use affects both water quality and our greenhouse gas footprint, and that we have to control what happens on land. In some catchments, meeting freshwater targets will involve combinations of mitigations such as riparian fencing and planting, treatment wetlands and denitrification filters. In other catchments, it may be necessary to de-stock or change to lower footprint enterprises.”

“But it’s no good just shutting down half of New Zealand’s export income,” added Chris Tanner, NIWA’s principal scientist for aquatic pollution. “You’ve got to find a positive way to solve this.”

Tanner, who co-leads the challenge’s innovative and resilient land use theme, says part of the problem is the fact that land values have not reflected the cost of environmental impacts. “Two properties, one very leaky and the other which retains contaminants, are likely to be valued the same if they produce the same milk solids per hectare,” he said.

Perhaps all land in New Zealand is overpriced relative to what can be produced from it, he added, because the costs of mitigating environmental damage haven’t been taken into account.

“The whole system has been allowed to drift,” he said, “because it’s hard, and it takes political will, and it’s against the tide of growth incentives. But the further out you get on a limb, the harder it is to come back.”

But come back we must. For Tanner, that means learning to look at land in a different way—“not just at how many kilograms of milkfat per hectare it might yield, but asking, ‘How susceptible is it to contaminant loss? Where are the water and contaminants moving, where are the critical leakage points, where can I achieve the best contaminant reductions?’”

“I dream of a public that appreciates that the world is complex. I know they want it in black and white and they want it in six seconds, but the truth is that’s not how the environment works.”

As for the soul-searching, well, we’ve been there before. It is almost 100 years since Herbert Guthrie-Smith, a Hawke’s Bay sheep farmer, published his magnum opus, Tutira, regarded by some as the greatest book ever written on New Zealand farming (though that’s like saying Moby-Dick is a book on whaling).

Guthrie-Smith was a man who started out believing “a man’s first duty is to the soil”. A few years before he died, he wrote an introduction to the third edition of Tutira that he called “the melancholy musings of a sheep farmer in concern of his soul”. Reflecting on a lifetime’s work on the land, he asked, “Have I for 60 years desecrated God’s earth and dubbed it improvement?”

We are still asking, and answering, that question.

The case of the vanishing nitrate

A lush dairy pasture right next to the Manawatu River—how could that not be a problem? I could almost see the nitrate leaching into the river. A classic case of unsuitable land use, I thought.

And I was wrong. Next to where I was standing, an apparatus was sucking and squirting groundwater from a pipe buried six metres deep in the pasture, measuring several water-quality parameters and sending them to a smartphone in Ranvir Singh’s hand. The screen showed the evidence: dissolved oxygen concentrations were minimal, and dropping as I watched.

Low dissolved oxygen in groundwater is an indicator of nitrate attenuation, or removal. This land happens to have a groundwater composition that naturally converts nitrate to gaseous nitrogen. ‘Benign denitrification’, it’s called. On land like this you can have intensive agricultural production without leaching nitrate to waterways.

Singh, a lecturer in environmental hydrology and soil science at Massey University, gave me a quick summary of the nitrogen cycle as it pertains to pasture. Gaseous nitrogen is industrially fixed as ammonia, which is processed into urea and applied as fertiliser. There it is naturally converted to nitrate, a form plants can use.

But they may not be able to use all of it—especially if it is accompanied by the massive amounts of nitrogen deposited in animal urine patches. This unused nitrate leaks into groundwater and waterways where it boosts the growth of algae—a major problem for freshwater ecosystems that have evolved to function in a low-nutrient environment.

Where oxygen levels in groundwater are low, however, microbes which prefer to consume dissolved oxygen switch to nitrate if oxygen is not available, converting it to gaseous nitrogen. It returns to the atmosphere where the journey began.

This capacity to attenuate nitrogen is highly variable across a catchment, Singh said. “You might go to one dairy farm, use a piezometer and find there is hardly any nitrate in the groundwater. You go to another farm, do the same measurement at the same depth, and you find nitrate. This leads you to conclude that some parts of a catchment are contributing disproportionately to river contamination.”

The implications are significant. As subsurface denitrification becomes better understood, it may be possible to say that in some parts of a catchment nitrate leaching won’t be a problem, while in other, leakier parts of the catchment mitigation measures will be needed.

“We could map the denitrification potential of catchments and then strategically use those maps to keep animals in different places at different times,” said Singh. “By reducing the loading in sensitive areas and increasing it in resilient areas, productivity could be maintained and water quality improved across the system.”

The doctor will see your river now

I was standing with Roger Young on a promontory overlooking Tasman Bay. A few hundred metres away, the Motueka River was pushing a plume of fresh water into the sea. Young knows this river intimately. He was part of an 11-year study of the Motueka catchment, which, at 2000 square kilometres, is larger than Stewart Island. In that study, Young, a freshwater ecologist with Nelson’s Cawthron Institute, focused on ecosystem health. There were, to put it mildly, issues.

In the headwaters, a traditional pastoral farming area, he measured the bacterial load downstream of where cattle crossed the Sherry River tributary. Concentrations shot up fourfold after cattle had crossed. Swimming was a health risk, but the locals were unaware.

Other rivers in the region were suffering, too. In 2001, the Waimea—heavily over-allocated for irrigation—ran dry. The Maitai, which runs through Nelson and supplies the city with drinking water, was experiencing periodic growths of the mat-forming cyanobacterium Phormidium, which is toxic enough to kill a dog.

Young began thinking about how ecologists might apply lessons from human medicine to freshwater systems. Earlier this year, he published a paper with Spanish and German colleagues entitled: ‘River doctors: Learning from medicine to improve ecosystem management’. Some of the principles they found applicable included the following:

Understand the patient’s medical history. Have there been disruptive events such as floods, earthquakes, toxic spills or landslides in the river’s past? Could previous land uses (such as mines) still be affecting river health?

Identify the cause before prescribing a cure. Treating the symptoms of river decline without locating the ultimate cause will not produce sustained health benefits.

Match treatments to desired outcomes (and resources). Is the aim to make the river swimmable? To restore its biodiversity? Is a one-time intervention such as removing a dam required, or are repeat treatments needed, such as restocking juvenile fish?

Monitor the outcome. In human health, follow-up is essential and monitoring (blood tests, regular check-ups) is standard. But with river restoration it rarely happens.

Practise preventive medicine. “Prevention is better than cure” is axiomatic in human health. But for most ecosystems, stresses and poor health are largely ignored unless there is an acute condition.

Young gave an example of how the cause of river pollution could be easily misdiagnosed. The Motueka’s sediment plume, which extends some five kilometres into Tasman Bay (an important commercial and recreational fishing area), was found to contain nickel and chromium contaminants. A survey of possible sources in the catchment pointed to a tanalising plant upstream. But on further research the minerals were shown to have arisen naturally from erosion in the river’s headwaters in the highly mineralised Red Hills.

Young believes that correct diagnosis coupled with professional support can lead not just to an immediate improvement in river health but long-term benefits in preventive care. In the Sherry River catchment, for example, the shock of landowners and residents at finding their beloved stream was, in fact, a microbial health hazard galvanised the community to form a catchment group.

Cattle crossings were bridged, leading to a 50 per cent improvement in water quality. Five kilometres of waterways were fenced, and 4000 trees, shrubs and grasses planted in riparian margins. Multiple other measures to control run-off and limit soil erosion were implemented, leading to the group receiving environmental awards in 2009 and 2013.

The community’s enthusiasm for their local river had another benefit: they published their story as a case history. Others can now refer to this “medical literature” and learn from the Sherry River experience.